content: /**
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
   * compliance with the License. You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License is
   * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
   * the License for the specific language governing permissions and limitations under the License.
   */
  
  package io.reactivex.observable.internal.operators;
  
  import java.util.*;
  import java.util.concurrent.Callable;
  
  import io.reactivex.common.functions.Function;
  import io.reactivex.observable.Observable;
  import io.reactivex.observable.SingleSource;
  
  /**
   * Helper utility class to support Single with inner classes.
   */
  public final class SingleInternalHelper {
  
      /** Utility class. */
      private SingleInternalHelper() {
          throw new IllegalStateException("No instances!");
      }
  
      enum NoSuchElementCallable implements Callable<NoSuchElementException> {
          INSTANCE;
  
          @Override
          public NoSuchElementException call() throws Exception {
              return new NoSuchElementException();
          }
      }
  
      public static <T> Callable<NoSuchElementException> emptyThrower() {
          return NoSuchElementCallable.INSTANCE;
      }
  
      @SuppressWarnings("rawtypes")
      enum ToObservable implements Function<SingleSource, Observable> {
          INSTANCE;
          @SuppressWarnings("unchecked")
          @Override
          public Observable apply(SingleSource v) {
              return new SingleToObservable(v);
          }
      }
      @SuppressWarnings({ "rawtypes", "unchecked" })
      public static <T> Function<SingleSource<? extends T>, Observable<? extends T>> toObservable() {
          return (Function)ToObservable.INSTANCE;
      }
  
      static final class ToObservableIterator<T> implements Iterator<Observable<T>> {
          private final Iterator<? extends SingleSource<? extends T>> sit;
  
          ToObservableIterator(Iterator<? extends SingleSource<? extends T>> sit) {
              this.sit = sit;
          }
  
          @Override
          public boolean hasNext() {
              return sit.hasNext();
          }
  
          @Override
          public Observable<T> next() {
              return new SingleToObservable<T>(sit.next());
          }
  
          @Override
          public void remove() {
              throw new UnsupportedOperationException();
          }
      }
  
      static final class ToObservableIterable<T> implements Iterable<Observable<T>> {
  
          private final Iterable<? extends SingleSource<? extends T>> sources;
  
          ToObservableIterable(Iterable<? extends SingleSource<? extends T>> sources) {
              this.sources = sources;
          }
  
          @Override
          public Iterator<Observable<T>> iterator() {
              return new ToObservableIterator<T>(sources.iterator());
          }
      }
  
      public static <T> Iterable<? extends Observable<T>> iterableToObservable(final Iterable<? extends SingleSource<? extends T>> sources) {
          return new ToObservableIterable<T>(sources);
      }
  
  }
  